Just finish replacing timing belt, water pump, crank/cam shaft seal, tensioner, tensioner spring, and thermostat on my 99 qx4. The truck has 161K miles and don't ask my why I waited so long. I brought the car used back in 02 and the owner manual said it has a chain. The used car dealership must gave us the wrong manual. This is my first timing belt change and took me about 10-12 hours to complete the job. It would probably be 2 hours less if I didn't screw up the crankshaft seal install. I have to drive around to look for a new seal.

Too my surprise, the timing belt is still in pretty good shape. No crack and any other obvious damage. It was very loose though. The water pump was making some noise and is probably on its way out. Only RH camshaft seal was showing a little oil leak. I also replace the bypass water hose behind the upper back timing belt cover as people suggested.

Overall the job is definitely doable for a weekend project. A good set of socket set and a good breaker bar will do. I have HF electrical impact gun but couldn't used it on the crankshaft bolt due to the clearance. I ended up using a 1/2" breaker bar and the starter method. You will also need an harmonic balancer puller and 2 m6x75mm screw.

Here are some photos:

Radiator off:


Trying to see how bad crankshaft bolt are:


Crankshaft blot off:


Where m6 screw goes for pulling off pulley:


Showup 3 hour lates for a cookout & softball game, still had fun:


Both top and bottom covers off:

nice!! i paid too much for a mechanic to do mine, i will do it next time!

PS since you dont have the manual, let me tell you the t-belt interval on these engines is 110k miles (not 60k like many japanese cars)

A little Googleing should find the correct owner's manual. You really want it. Print a copy to keep in the truck,
and keep the PDF on your computer.